The inventive concepts relate to a touch controller, and more particularly, to a touch controller having increased sensing sensitivity, and a display driving circuit and a display device and system including the touch controller.
As a consequence of the need for thinner and lighter display devices, flat display devices have replaced cathode ray tubes (CRTs). Examples of flat display devices are LCDs, field emission displays (FEDs), organic light emitting diodes (OLEDs), and plasma display panels (PDPs).
In general, such flat display devices include a plurality of pixels that are arranged in a matrix in order to display an image. In an LCD which is an example of flat display device, a plurality of scan lines that deliver a gate selection signal and a plurality of data lines that deliver gratin data are arranged to intersect one another, whereby a plurality of pixels are formed where the scan lines and the data lines intersect one another.
A touch screen panel, e.g., a capacitive touch screen panel, includes a plurality of sensing units. If a user touches a screen of the touch screen panel with his/her finger or a touch pen, a capacitance value of a corresponding sensing unit changes. In general, the touch screen panel is attached to an upper part of a flat display device, and when a user's finger or a touch pen approaches or touches the sensing units of the touch screen panel, the capacitance value of a corresponding sensing unit is provided to a touch screen processor. The touch screen processor senses a capacitance of the corresponding sensing unit by using the sensing lines, and determines whether the touch screen panel is touched with a user's finger or a touch pen or determines the touched location on the touch screen panel. The sensing units may be included in a display panel in order to minimize a reduction in yield and brightness and an increase in the thickness of the display panel, caused when the touch screen panel is attached to the display panel.
FIG. 1 is a block diagram of a general touch screen system 10. Referring to FIG. 1, the touch screen system includes a touch screen panel 11 having a plurality of sensing units and a signal processor 12 that senses and processes a change in a capacitance of each of the sensing units and then generates touch data.
The touch screen panel 11 includes a plurality of sensing units disposed in a row and a plurality of sensing units disposed in a column. Referring to FIG. 1, the touch screen panel 11 includes a plurality of rows in which a plurality of sensing units are disposed, in which a plurality of sensing units are arranged in each of the rows. The plurality of sensing units arranged in each of the rows are electrically connected to one another. Also, the touch screen panel 11 includes a plurality of columns in which a plurality of sensing units are disposed, in which a plurality of sensing units are arranged in each of the columns. The plurality of sensing units arranged in each of the columns are electrically connected to one another.
The signal processor 12 generates the touch data by sensing a change in the capacitance of each of the plurality of sensing units of the touch screen panel 11. For example, signal processor 12 may sense a change in the capacitance of each of the plurality of sensing units in the plurality of rows and in the plurality of columns in order to determine whether the touch screen panel 11 is touched with a user's finger or a touch pen, or to determine the touched location on the touch screen panel 11.
However, the plurality of sensing units of the touch screen panel 11 contain a parasitic capacitance component. Such a parasitic capacitance component may be classified into a horizontal parasitic capacitance component generated between a plurality of sensing units and a vertical parasitic capacitance component generated between a sensing unit and a display panel. If the whole parasitic capacitance has a large value, a change in the capacitance of a sensing unit touched by a user's finger or a touch pen has a relatively small value, compared to the value of the whole parasitic capacitance. The closer the user's finger or the touch pen approaches the sensing unit, the greater the capacitance value of the sensing unit. However, when the sensing unit has a large parasitic capacitance value, the sensing sensitivity of the sensing unit is lowered. Also, a change in an electrode voltage VCOM applied onto the display panel may cause a sensing noise to occur during the touching of the sensing unit through the vertical parasitic capacitance component.
In addition, the performance of the touch screen system 11 may be affected by various noise factors which are generated in an undesirable environment. Examples of the various noise factors are an electromagnetic noise in the air, a skin accumulated noise, and a noise generated in the touch screen system 10. Such noises may degrade the sensing sensitivity of the touch screen system 10.